test(backend): add matchmaking relevance and ranking tests

tests/TarninaHub.Tests/Matchmaking/StubMatchmakingService.cs

@@ -0,0 +1,25 @@
+using TarninaHub.Application.Abstractions;
+using TarninaHub.Application.Dtos;
+
+namespace TarninaHub.Tests.Matchmaking;
+
+public sealed class StubMatchmakingService : IMatchmakingService
+{
+    public Task IndexInnovationAsync(string innovationId, CancellationToken cancellationToken) =>
+        Task.CompletedTask;
+
+    public Task IndexProblemAsync(string problemId, CancellationToken cancellationToken) =>
+        Task.CompletedTask;
+
+    public Task IndexSubmissionAsync(string submissionId, CancellationToken cancellationToken) =>
+        Task.CompletedTask;
+
+    public Task<int> ReindexAsync(CancellationToken cancellationToken) =>
+        Task.FromResult(0);
+
+    public Task<MatchResponse?> MatchAsync(
+        string submissionId,
+        MatchRequest request,
+        CancellationToken cancellationToken) =>
+        Task.FromResult<MatchResponse?>(new MatchResponse([], [], true));
+}